Age of Peters Ammo Box

[mick56]

I have a few of these Peters ammo boxes and am wondering how old they are. I found a website, but it wasn't clear to me how old these are. Inside the flap are some numbers N 27 M 45, is this a date? The headstamp says Peters 30 USG.

 

[Ruchman]

Dating Cartridge Boxes By Peters Cartridge Company - International Ammunition Association
This may help